This is a simple program that moves around items in Super Metroid. It is used for racing the game.
When racing the game, it is suggested that each player play the same seed to ensure a level playing field.
When you start the program, you will see there are two tabs, one for "Current Randomizer" and one for "Old Randomizer". "Old Randomizer" is just for the people who have been playing randomizer for a while and really miss the old days.
If you've beaten Super Metroid once or twice, I suggest you play "Casual". If you are a speedrunner, "Speedrunner" is probably the correct difficulty for you. If you hate yourself, "Masochist" seems most appropriate.
This is a very important trick to know! It will allow for so many new areas to be open to you. Here's a short demo: https://www.youtube.com/watch?v=C5FlyJod8qk
If you drew Speed Booster as your first item, this move is mandatory. Just wait to press run when building a charge, like so: https://www.youtube.com/watch?v=rNV9yS6xvas
This will enable you to make it past the bomb blocks in the room left of your ship (simply wait about half a second to press run, then jump into the block with blue speed.)
Going to Wrecked Ship early is pretty good in Randomizer, so knowing how to get across without using Grapple or Speed Booster is pretty important. Here's a demonstration: https://www.youtube.com/watch?v=4HVhTwwax6g
This will allow you to enter lower Norfair without the use of Space Jump. Here's a demonstration: https://www.youtube.com/watch?v=nK1phV5WRPA
This is a technique allowing you to open green gates and wave gates without wave beam, both from the "wrong" side. The Green Gate Glitch is also valid on blue gates, allowing you to retrace your steps from red Brinstar to green Brinstar, as well as sneak past to get whatever is hiding in Screw Attack's spot. Here's a demo: https://www.youtube.com/watch?v=7I2Ff1dafEI
You can also open right facing gates from the "wrong" side in certain circumstances, as shown here: http://www.twitch.tv/dessyreqt/c/4390398
Probably you will want to know this with how little ammo there is in randomizer nowadays. Here's an entire article on the subject: https://wiki.supermetroid.run/Mother_Brain_Room#Zebetite_Glitch